DE10311075B4 - Process for purifying an ester compound - Google Patents

Abstract

A process for purifying an ester compound comprising the adsorption treatment of the ester compound obtainable by reacting a fatty acid derived from natural fats and oils with an alcohol having 1 to 4 carbon atoms with at least one adsorbent, adsorbent A selected from the group consisting of clay and activated carbon, further comprising the adsorption treatment with a hydrogenation decomposition type adsorbent comprising Ni and / or Cu, adsorbent B, in hydrogen gas or a mixed gas of hydrogen gas and an inert gas, and the treatment with the absorbent B after the treatment with the adsorbent A.

Description

This invention relates to a process for purifying an ester compound and a use of the ester compound.

An ester of a fatty acid derived from natural fats and oils and a lower alcohol of 1 to 4 carbon atoms usually contains sulfur in a concentration of at least 2 to 10 mg / kg. When such an ester is hydrogenated in the presence of a hydrogenation catalyst to produce an alcohol, the sulfur content contained in the ester acts as a catalyst poison on the hydrogenation catalyst to reduce the activity of the catalyst. In particular, in a continuous fixed bed reaction, the life of the catalyst is greatly shortened, and therefore the catalyst should be changed frequently, thereby reducing the work efficiency of the equipment.

Various studies have been conducted to remove the sulfur content as catalyst poison for the hydrogenation catalyst. For example, because sulfur compounds have a relatively high boiling point, a method of reducing sulfur concentration by distillation is often used. However, the removal of all the sulfur compounds by distillation is not possible, and to reduce the sulfur concentration to a low level of about 0.5 mg / kg, originally required high-boiling components should be discarded in large quantities, resulting in a remarkable reduction in yield.

The molybdenum and tungsten based desulfurization catalysts used in the petrochemical industry require high temperatures of 300 ° C or more. When esters of fatty acids derived from the natural fats and oils are subjected to hydrogenation treatment such as high temperatures, fatty acids and other decomposed products are formed in large quantities as by-products during the course of hydrogenation decomposition of the ester groups, so that problems of deterioration of qualities of Esters result.

In order to solve the problems described above, a method for hydrogenation decomposition of sulfur compounds in a hydrogen atmosphere and the subsequent adsorption on an adsorbent containing a metal such as Ni and Cu, for example, in U.S. Pat Japanese Patents 2544552 and 2934073 described. However, in order to maintain the intended adsorption performance, the expensive adsorbent should be replaced frequently, or large adsorption plants should be installed, resulting in higher costs in the adsorption treatment.

JP-6-33086-A1 shows the desulfurization that is performed by the fats and oils and silica gel. Out DE 4 131 209 A1 For example, a process for producing an alcohol is known in which fats and oils or fatty acid esters are reduced with hydrogen in the presence of a catalyst. DE 42 17 839 A1 describes a process for preparing desulfurized fats and oils or fatty acid esters by using a catalyst of the formula: Ni · Cu _x O _y , wherein x has a value of 0.02 to 8 and y is an atomic ratio of oxygen satisfying the valence requirements of Ni and Cu are sufficient.

The object of this invention is to provide a process for purifying a low sulfur ester compound obtainable from a fatty acid derived from natural fats and oils and a lower alcohol having from 1 to 4 carbon atoms, without a deterioration in selectivity and a reduction the yield due to the formation of by-products, etc., as well as a use for producing an alcohol without decreasing the activity of the catalyst.

This invention provides a process for purifying an ester compound according to claim 1.

The invention also provides a use of the ester compound obtained by the above-mentioned process for producing an alcohol by hydrogenating the ester compound.

The production of an ester from a fatty acid derived from natural fats and oils and a lower alcohol having 1 to 4 carbon atoms is carried out by transesterification between natural fats and oils and a lower alcohol having 1 to 4 carbon atoms.

The natural fats and oils used herein include animal fats and oils such as tallow and fish oil and vegetable fats and oils such as palm kernel oil, coconut oil, palm oil, soybean oil and rapeseed oil. In particular, fats and oils containing C _8-22 fatty acids are preferred as constituent fatty acids, and vegetable fats and oils are particularly preferred.

The lower alcohol of 1 to 4 carbon atoms includes methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, etc.

The transesterification can be carried out by any known method. For the reaction, a continuous reaction system or a batch-operated system may be employed, but if the ester is produced in large quantities, the continuous reaction is preferred. As the transesterification catalyst, a homogeneous alkali catalyst such as sodium hydroxide, potassium hydroxide and sodium alcoholate is generally used, but a solid catalyst such as an ion exchange resin, hydrous zirconium hydroxide, aluminum phosphate and sulfuric acid doped zirconia, titanium silicate may also be used. When the homogeneous alkali catalyst is used, the reaction is generally carried out under the following conditions. The reaction temperature is 30 to 90 ° C, preferably 40 to 80 ° C, and the reaction pressure is in the range of atmospheric pressure to 0.5 MPa, and preferably, the reaction is carried out at atmospheric pressure. From the viewpoint of cost and reactivity, the lower alcohol having 1 to 4 carbon atoms is preferably used in an amount of 1.5 to 10 moles per mole of the starting fats and oils. When free fatty acids are contained in the starting fats and oils, it is also effective that before the transesterification with the alkali catalyst, the fatty acids are previously esterified by burning an acid catalyst such as sulfuric acid and p-toluic acid.

The ester in this invention is useful as an ester used for the production of an alcohol obtained, in particular, by catalytic reaction.

The thus obtained ester of a fatty acid derived from natural fats and oils and a lower alcohol having 1 to 4 carbon atoms is subjected to adsorption treatment with the adsorbent "A", whereby an ester having a low sulfur concentration can be produced.

As the adsorbent "A", clay or activated carbon, which are commercially available and inexpensive, are used, and loam is preferable. The clay comprises, for example, active clay or acid clay consisting essentially of naturally occurring montmorilonite-based clay or a purified product of such clay and synthetic clay, and in view of the cost and adsorption performance, active clay and acid clay are preferable.

Depending on the adsorption treatment system and the shape of the reaction unit, the shape of the adsorbent "A" may be properly selected from powdery, spherical and cylindrical moldings. As the adsorption treatment system, the continuous, semi-batch or batch system may be employed, and in the continuous treatment, the suspension system or a fixed bed system may be used.

The temperature for the adsorption treatment with the adsorbent "A" is preferably 10 to 150 ° C, more preferably 30 to 130 ° C from the viewpoint of suppression of side reactions such as ester decomposition. In the bleaching treatment of fats and oils with active clay, the treatment is generally carried out under dehydration treatments such as high temperature, reduced pressure, but sulfur adsorption is intended in this invention, and thus the dehydrating conditions are not necessarily required and sufficient adsorption at low temperatures such as about room temperature possible. The pressure may be atmospheric or reduced pressure to perform this treatment.

The atmospheric gas in the treatment is not limited, and an arbitrary atmospheric gas such as air, inert gas such as nitrogen or argon, hydrogen gas or a mixed gas thereof may be selected. When the treatment is performed only with the adsorbent "A", air or nitrogen is preferable.

The amount of the adsorbent "A" is preferably 0.01 to 10.0 wt%, more preferably 0.1 to 3.0 wt%, still more preferably 0.2 to 2.0 wt% for use, based on the ester.

It is known in the art to carry out the adsorption treatment (treatment with active clay) of fats and oils, but their effect on the removal of sulfur compounds is small. On the other hand, the adsorption treatment of the ester unfolds from a fatty acid derived from fats and oils and a lower alcohol having 1 to 4 carbon atoms with the adsorbent "A". a significant effect on the removal of sulfur compounds. The reason is probably that the lower alcohol ester is superior to the fats and oils as a solvent for the adsorption of sulfur compounds, and that those contained in the lower alcohol ester are compared with sulfur compounds present in fats and oils Sulfur compounds are present in such a form that they can be readily adsorbed.

It is also effective that the ester of a lower alcohol before or after the adsorption treatment with the adsorbent "A" is subjected to distillation for removing impurities and further reducing the concentration in such a range that the yield does not decrease.

In the present invention, an ester having a further lowered sulfur concentration is produced by an adsorption treatment with the adsorbent "B" in hydrogen or a mixed gas atmosphere of hydrogen and an inert gas in combination with the above adsorption treatment step with the adsorbent "A". The method of carrying out the adsorption treatment with the adsorbent "A" and then the adsorption treatment with the adsorbent "B" for carrying out this invention is effective.

The adsorbent "B" used in the invention is a hydrogenation decomposition type adsorbent comprising Ni and / or Cu which hydrogenates and decomposes sulfur compounds to adsorb them as sulfides. Usually, the adsorbent "B" is preferably an adsorbent supported on or mixed with carriers, and the Ni content is preferably 10 to 200% based on the carrier component, and the atomic ratio of Cu to Ni (Cu / Ni) is preferably 0 to 8. The carriers used herein are selected from known supports such as silica, alumina, silica-alumina, zeolite, diatomaceous earth, active clay, titania, zirconia and activated carbon. The shape of the adsorbent "B" is suitably selected from powdery, spherical and cylindrical moldings depending on the adsorption system.

As the adsorbent treatment system with the adsorbent "B", any commonly used systems such as suspension systems and fixed bed system can be used. In a large scale treatment, a continuous packed bed system is advantageous.

When the adsorption treatment is carried out continuously in a fixed bed system, the treatment is carried out under the following conditions. The atmospheric gas is preferably hydrogen or a mixed gas of an inert gas with 1 volume% or more of hydrogen, and the inert gas includes nitrogen, argon, helium or methane. The flow rate of hydrogen or a hydrogen mixed gas is preferably set in such a range that the molar ratio of hydrogen to the ester group is 0.1 to 300, and the molar ratio of the saponification value of the treated ester is calculated. The pressure of the atmospheric gas is preferably 0.01 to 50 MPa, more preferably 0.1 to 30 MPa. From the viewpoint of achieving a sufficient adsorption rate, the treatment temperature is preferably 40 ° C or more, more preferably 50 ° C or more. In view of the suppression of side reaction such as hydrogenation decomposition, the treatment temperature is preferably 250 ° C or less, and more preferably 200 ° C or less. The hourly liquid space velocity (LHSV) of the ester is preferably 0.1 or more from the viewpoint of improving productivity and suppressing side reactions such as hydrogenation decomposition, and at the same time, LHSV is 5 or less from the viewpoint of achieving sufficient adsorption performance.

When the ester treated with the adsorbent "A" is subsequently subjected to adsorption treatment with the adsorbent "B", the adsorption rate thereof with the adsorbent "B" is significantly increased as compared with the adsorption rate when the ester does not react with the adsorbent "A". is treated, but the adsorption treatment with the adsorbent "B" is subjected. This effect of improving the adsorption rate means that sulfur compounds hardly adsorbed on the adsorbent "B" are selectively (or preferably) adsorbed on the adsorbent treatment with the adsorbent "A". That is, the most notable effect of this invention is to add to the selectivity of the sulfur compounds for adsorption in the respective steps, i. the step of the adsorption treatment with the adsorbent "A" and the step of the adsorption treatment with the adsorbent "B", and by the combination of the respective steps, an ester having a further lowered sulfur content can be produced.

Another advantage achieved by combining the adsorption treatment steps with the adsorbents "A" and "B" is that the adsorption loading of the expensive adsorbent "B" can be significantly reduced. For example, if the adsorbent "B" is used directly in the suspension system, the amount of the adsorbent used can be reduced and the treatment time can be shortened and the treatment conditions can be made moderate. On the other hand, when used in the packed bed system, the amount of the adsorbent used can be reduced and the life of the adsorbent "B" can be significantly improved. The adsorption performance of the adsorbent "B" can be proved to a maximum extent in small plants for a prolonged period of time without the need for the frequent replacement of the expensive adsorbent "B", causing a significant cost reduction.

The low sulfur ester produced by this process is particularly useful as a starting material for producing an alcohol by hydrogenation reaction in the presence of a hydrogenation catalyst. Because of the low sulfur content, there is less drop in the activity of the hydrogenation catalyst, and especially in the continuous fixed bed reaction, the life of the catalyst can be significantly improved.

Hereinafter, the process for producing an alcohol by hydrogenating the low sulfur ester produced according to the present invention will be described.

As the hydrogenation catalyst, well-known catalysts based on copper and noble metals such as palladium and platinum are used. The copper-based catalysts include copper-chromium, copper-zinc, copper-iron-aluminum and copper-silica. In the presence of any of the catalysts described, the hydrogenation reaction may be carried out in any of the reaction systems used, such as a liquid phase suspension bed system and a fixed bed system.

When the reaction is carried out in the liquid-phase suspension bed system, although the amount of the catalyst is preferably 0.1 to 20% by weight based on the ester, it may be arbitrarily selected in such a range as to obtain the practical reaction yield. depending on the reaction temperature or the reaction pressure. The reaction temperature is preferably 160 to 350 ° C, more preferably 200 to 280 ° C. The reaction pressure is preferably 0.1 to 35 MPa, preferably 3 to 30 MPa.

When the reaction is carried out continuously in the fixed bed system, the catalyst is used in a cylindrical, pellet or spherical form. The reaction temperature is preferably 130 to 300 ° C, more preferably 150 to 270 ° C, and the reaction pressure is preferably 0.1 to 30 MPa. In view of productivity and reactivity, the LHSV value is arbitrarily determined depending on the reaction conditions.

In the present invention, a lower alkyl ester can be produced from a fatty acid derived from natural fats and oils of low sulfur content and at a lower cost without deteriorating the selectivity and reacting the yield due to the formation of by-products. Further, an alcohol can be produced from the ester obtainable by the process of the present invention as a starting material without lowering the activity of the catalyst.

This invention will be explained in more detail by way of examples.

The measurement of sulfur concentrations in the examples was carried out using the analyzer for measuring the total sulfur content in trace amounts of 7000 TS of ANTEK Co., Ltd. carried out.

Example 1 (reference)

24% by weight of methanol, 0.10% by weight of 98% sulfuric acid was added to palm kernel oil previously treated with active clay (0.5% WAC REGULAR 1B (Trade Mark), manufactured by TAIKO CLAY MARKETING SDN, BHD, 115 ° C , 15 kPa), and the mixture was reacted at 70 ° C for 1 h. Subsequently, the formed glycerol layer was removed while adding 0.30 wt.% Of caustic soda and 10 wt.% Of methanol in 3 divided portions to the palm kernel oil and reacting at 50 ° C for 3 hours. After the reaction, the oil layer was washed with water to obtain a palm kernel oil fatty acid methyl ester. The resulting palm kernel oil fatty acid methyl ester was further distilled to obtain a palm kernel oil fatty acid methyl ester having a sulfur concentration of 0.75 mg / kg.

$$\text{Adsorptionsgrad}\left(\%\right)=\left({\text{s}}_{\text{0}}{\text{-s}}_{\text{1}}\right)\times 100/{\text{s}}_{\text{0}}$$

50 g of the above methyl ester and active clay manufactured by Mizusawa Kagaku Kogyo Co., LTd. (Trade name: Gareon Earch NS), 0.5 g (1.0% by weight based on the methyl ester) was placed in a 100 ml flask and stirred at 60 ° C for 90 minutes under atmospheric pressure. The active clay was removed by filtration and the concentration of sulfur in the methyl ester was measured and the reduction in the amount of sulfur and the degree of adsorption were determined by the following formulas. The results are shown in Table 1. $$\text{Reduction in the amount of sulfur}\left(\text{mg / kg}\right)={\text{s}}_{\text{0}}{\text{-s}}_{\text{1}}$$

$$\text{adsorption}\left(\%\right)=\left({\text{s}}_{\text{0}}{\text{-s}}_{\text{1}}\right)\times 100/{\text{s}}_{\text{0}}$$

In the formulas, S _{0 is} the concentration of sulfur (mg / kg) before the adsorption treatment with the adsorbent "A" and S _{1 is} the concentration of sulfur (mg / kg) after the adsorption treatment with the adsorbent "A".

Example 2 (reference)

The adsorption treatment was carried out in the same manner as in Example 1, except that the amount of the active clay (Gareon Earch NS) was 0.5% by weight, based on the methyl ester, and the reduction of the amount of sulfur and the adsorption degree were determined in the same way. The results are shown in Table 1.

Example 3 (reference)

The adsorption treatment was carried out in the same manner as in Example 1 except that the amount of the active clay (Gareon Earth NS) was 3.0% by weight based on the methyl ester and that the treatment time was set to 180 minutes, and the reduction of the sulfur amount and the adsorption degree were determined in the same way. The results are shown in Table 1.

Example 4 (reference)

The adsorption treatment was carried out in the same manner as in Example 1 except that activated carbon (trade name: YP-17) manufactured by Kuraray Chemical Co., Ltd. was used. in an amount of 1.0% by weight, based on the methyl ester, and the reduction of the sulfur amount and the adsorption degree were determined in the same manner. The results are shown in Table 1.

Comparative example

The adsorption treatment was carried out in the same manner as in Example 1, except that silica alumina (trade name: KW # 700) manufactured by Kyowa Chemical Industry Co., Ltd. consisting of silica and alumina was the same as active clay in one Amount of 1.0 wt.%, Based on the methyl ester was used and the reduction of the sulfur amount and the adsorption degree were determined in the same way. The results are shown in Table 1. Table 1 adsorbent Adsorbent amount (% by weight based on the ester) Treatment time (min) Reduction in the amount of sulfur (mg / kg) Adsorption degree (%) Ex.1 * Active clay (Gareon Earth NS) 1.0 90 0.28 37 Ex.2 * Active clay (Gareon Earth NS) 0.5 90 0.22 29 EX3 * Active clay (Gareon Earth NS) 3.0 180 0.39 52 EX4 * Activated carbon (YP-17) 1.0 90 0.15 20 Vgl.Bsp.1 Silica-Alumina (KW # 700) 1.0 90 0.02 3 *Reference

As can be seen from Table 1, the sulfur concentration in the examples was significantly reduced despite the pretreatment of the fats and oils with active clay.

Example 5

The methyl ester was subjected to adsorption treatment with the adsorbent "A" under the same conditions as in Example 1, except that the amount of the methyl ester was 300 g, the amount of the active clay (Brand: Gareon Earth NS) 3.0 g (1 , 0% by weight, based on the methyl ester) and that the treatment time was 180 minutes, and the thus treated methyl ester (sulfur concentration 0.42 mg / kg) was subjected to the following adsorption treatment with the adsorbent "B".

worin S₀ die Konzentration des Schwefels (mg/kg) in 0 h und S_t die Konzentration an Schwefel (mg/kg) in t Stunden ist.As adsorbent "B", 2.0 g (1.0% by weight, based on the methyl ester) of Ni / silica alumina (trade name: C46-7RS, composition: Ni = 52%, silica-alumina carrier 38%; 1/16 inch diameter extruded product made by SÜD-CHEMIE Inc.) was placed in a basket, which was then connected to a stir bar in a 500 ml autoclave. 200 g of the above methyl ester treated with the adsorbent "A" was placed in the autoclave, the atmosphere in the autoclave was replaced by hydrogen and the methyl ester was then heated to 135 ° C under hydrogen flow at 10 l / min. After the temperature reached 135 ° C, hydrogen was introduced to increase the pressure to 24.5 MPa, and at this stage, the adsorption treatment time was regarded as zero. During the treatment samples were taken and the adsorption treatment was carried out for a total of 120 minutes. From the sulfur concentrations in the samples, the adsorption rate was determined according to the following formula. The results are shown in Table 2. $$\text{Adsorptionsrage}=\text{ln}\left({\text{s}}_0/{\text{s}}_{\text{t}}\right)/\text{t}$$

where S _{0 is} the concentration of sulfur (mg / kg) in 0 h and S _{t is} the concentration of sulfur (mg / kg) in t hours.

Comparative Example 2

200 g of the methyl ester (sulfur concentration 0.75 mg / kg) to which no adsorption treatment with the adsorbent "A" used in Example 1 was subjected was subjected to adsorption treatment with the adsorbent "B" under the same conditions as in Example 5, and the adsorption rate was determined in the same manner. The results are shown in Table 2. Table 2 Methyl ester before the adsorption treatment with the adsorbent "B" Sulfur concentration (mg / kg) Adsorption rate (h ^-1 ) Example 5 Treated with active clay; Sulfur concentration 0.42 mg / kg in 0 h 0.30 in 1 h 0.01 3.4 Vgl.Bsp.2 Not treated with the adsorbent "A"; Sulfur concentration 0.75 mg / kg in 0 h 0.74 in 2 hours 0.05 1.3

Example 6

24% by weight of methanol and 0.10% by weight of 98% sulfuric acid were added to crude coconut oil and reacted at 70 ° C. for 1 h. Thereafter, the formed glycerol layer was removed while adding 0.25% by weight of caustic soda and 9% by weight of methanol in 3 divided portions to the coconut oil and reacting at 50 ° C for 4 hours. After the reaction, the oil layer was washed with water to obtain a coconut methyl fatty acid ester having a sulfur concentration of 2.8 mg / kg.

2000 g of the resulting coconut oil fatty acid methyl ester were placed in a 3 L flask and 10 g of active clay (trade name: PAGODA, PT MADU LINGGA PERKASA Co., Ltd.) (0.5% by weight, based on the methyl ester) were added as the adsorbent "A". added and stirred at 60 ° C at atmospheric pressure for 1 h. The sulfur concentration in the methyl ester in a filtrate obtained by filtration was 2.1 mg / kg.

1700 g of the above methyl ester treated with the adsorbent "A" was distilled (bottom cut). The distillation conditions were as follows: Sulzer packing (number of theoretical stages = 5) was used; Reflux ratio = 1; final soil temperature, 240 ° C; Column top pressure 0.8 kPa, distillation yield 97%. The sulfur concentration in the methyl ester after distillation was 0.53 mg / kg.

Subsequently, the adsorption treatment with the adsorbent "B" was carried out in the same manner as in Example 5, except that a bottom-cut methyl ester was used, and the adsorption rate was determined. The results are shown in Table 3.

Comparative Example 3

A coconut oil fatty acid methyl ester (sulfur concentration 2.8 mg / kg) obtained by transesterification of the crude coconut oil with methanol in the same manner as in Example 6 was subjected to distillation (bottom cut) under the same conditions without adsorption treatment with the adsorbent "A". The sulfur concentration in the methyl ester after distillation was 0.78 mg / kg.

Subsequently, the adsorption treatment with the adsorbent "B" was carried out in the same manner as in Example 5, except that this bottom-cut methyl ester was used and the adsorption rate was determined. The results are shown in Table 3. Table 3 Methyl ester before the adsorption treatment with the adsorbent "B" Sulfur concentration (mg / kg) Adsorption rate [h ^-1 ] Example 6 distilled after treatment with active clay sulfur concentration 0.53 mg / kg in 0 h in 1 h 3.5 0.32 0, 01 Vgl.Bsp.3 distilled, unreacted methyl ester, sulfur concentration 0.78 mg / kg in 0 h in 1 h 2.4 0.44 0.01

Example 7

A coconut oil fatty acid methyl ester obtained by transesterification of a crude coconut oil with methanol in the same manner as in Example 6 was subjected to an adsorption treatment with active clay (same adsorbent "A" as in Example 6) in an amount of 0.5% by weight based on the methyl ester , at 60 ° C, atmospheric pressure and for 1 h subjected. After the filtration, distillation was conducted to obtain a methyl ester fraction having a sulfur concentration of 1.4 mg / kg.

This methyl ester fraction was subjected to adsorption treatment with the adsorbent "B" and sequentially to a hydrogenation reaction in a fixed bed reaction unit under the following conditions: The fixed bed reaction unit was equipped with 2 columns in series, wherein the first column was packed with 200 ml Ni / silica alumina (same adsorbent). B "as in Example 5) and the second column with 400 ml of copper-zinc catalyst supported on titania (composition: Cu = 35%, Zn = 1.8%, 50% TiO _{2 support} , Form: 3 , 2 mm ∅ × 3.2 mm cylindrical shape) was loaded. The conditions for adsorption on the first column loaded with the adsorbent "B" were such that the pressure was 19.6 MPa, the temperature was 90 ° C, and the feed rate of the methyl ester was 400 ml / hr. The concentration of sulfur in the methyl ester after treatment with the first column was 0.25 mg / kg.

The conditions for the hydrogenation reaction in the second column loaded with the hydrogenation catalyst were such that the pressure was 19.6 MPa and the temperature was 220 ° C. The GC yield of an alcohol obtained after the hydrogenation reaction was 93.7% and the saponification value was 15.2 mg KOH / g.

Claims (5)

A process for purifying an ester compound comprising the adsorption treatment of the ester compound obtainable by reacting a fatty acid derived from natural fats and oils with an alcohol having 1 to 4 carbon atoms with at least one adsorbent, adsorbent A selected from the group consisting of clay and activated carbon, further comprising the adsorption treatment with a hydrogenation decomposition type adsorbent comprising Ni and / or Cu, adsorbent B in hydrogen gas or a mixed gas of hydrogen gas and an inert gas wherein the treatment with the absorbent B is carried out after the treatment with the adsorbent A. Method according to Claim 1 wherein the adsorbent A is clay. Method according to Claim 1 wherein the adsorbent A is an active clay or acid clay. Method according to one of Claims 1 to 3 wherein the adsorption treatment with the adsorbent A is carried out at 10 to 150 ° C. Use of the ester compound obtainable by the method of any one of Claims 1 to 4 for producing an alcohol by hydrogenating the ester compound.